Polypropylene monofilament sutures

ABSTRACT

A flexible, uniform monofilament of isotatic polypropylene having an improved hand and an ultimate elongation greater than 35 percent is prepared by extruding isotatic polypropylene having a weight average molecular weight between 299,000 and 316,000 to form a monofilament, stretching said monofilament at 300* F. to about 6.6 times its original length, and subsequently permitting the stretched monofilament to contract to between 91 percent and 76 percent of its stretched length.

United States Patent [72] inventor Gregory J. Listner 3,106,442 10/1963Compostella et a1. 264/290 Kendall Park, NJ. 3,152,380 10/1964 Martin264/290X [21] AppLNo. 846,412 3,359,983 12/1967 Northey 128/3355 [22]Filed July 31,1969 3,413,397 11/1968 Bierbaum et a1 264/342 :ZZESZ: g gii Primary Examiner-Dalton L. Truluck Somerviue, J A!!0rneys Robert W.Kell and Robert L. Mmler ABSTRACT: A flexible, uniform monofilament ofisotatic [54] :PNOFILAMENT SUTURES polypropylene having an improved handand an ultimate elonrawmg gation greater than 35 percent is prepared byextruding [52] U.S.Cl 128/3355, isolatic polypropylene having a weightaverage molecular 161/150, 161/161 weight between 299,000 and 316,000 toform a monofila- [51] 1nt.Cl A611 17/00 ment. Stretching said mo fi a300 to about [50] Field ofSearch 128/3355; times its original length. nu q n ly p rmi ing h 161/150, 175;264/210 F, 290, 342R stretchedmonofilament to contract to between 91 percent and 76 percent of itsstretched length. [56] References Cited UNITED STATES PATENTS 3,105,49310/1963 Usher 128/3355 Jf /'e s5J.' /'a/ CZ/rre '0 i o k .f/oayaf/bnPATENTED DEC28 I97! SHEET 2 [1F 5 INVENTOR. .CPiqa/vy J l/sr/vmflllllllnllllllllllllll'llll A TTU/f. Iii

PATENTED UEB28 Ian SHEET 0F 5 Z/li PATENTEU M62819?! 3.630.205

SHEET 5 or 5 ATTORNEY 1 POLYPROPYLENE MONOFILAMENT SUTURES BACKGROUND OFTHE INVENTION are of the second type; i.e. they are nonabsorbable in thehuman body.

The strongest polypropylene monofilaments can generally be made fromresins of high molecular weight and high crystallinity. The processingconditions along with the resin physical properties determine the finalfilament properties, and it is known that to obtain the tenacity that isrequired of a surgical suture, the extruded polypropylene monofilamentmust be stretched to alignthe polymer molecules.

Some of the advantages of oriented isotatic polypropylene as a suturematerial are described in US. Pat. No. 3,359,983. Isotatic polypropylenemonofilarnentis so highly inert that minimal tissue reaction occurs inthe suture area.

It has long been recognized that the drawing or stretching ofpolypropylene monofilament that is required to impart the necessarytenacity for suture use reduces the flexibility of the resulting productand results in poor handling qualities. While the handlingcharacteristics of the suture are difficult to define, a suture shouldnot be wiry or stiff and should remain in the position in which it isplaced until moved by the surgeon. I

Generally speaking, a stiff suture that has poor handlingcharacteristics is inelastic and will break upon stretching. Thepolypropylene sutures of the prior art were characterized by an ultimateelongation (the percent increase in the length of the monofilament whenstretched at room temperature to the breaking point) of less than 25percent. By contrast, the flexible polypropylene monofilaments of thepresent invention are characterized by an ultimate elongation of 35 toabout 63 percent.

It is another disadvantage of the polypropylene monofilaments previouslyknown that they exhibit memory and will tend to retain the shape of thepackage. Stated in another way, a monofilament that is packaged as acoil will to a large extent retain the coil form after removal from thepackage. This makes it difficult for the surgeon to handle and tie downthe monofilament particularly in the large sizes, i.e., size 2/0 andabove.

These problems have been resolved by the present invention which enablesone to manufacture a polypropylene monofilament suture of satisfactorytenacity and knot strength while retaining the percent elongation andflexibility that is demanded by the surgeon.

SUMMARY 'OF THE INVENTION It has now been discovered that theflexibility of an extruded, isotatic polypropylene suture can be greatlyimproved with little sacrifice in tensile strength by stretching undercontrolled conditions to about 6.6 times the original extruded lengthand then relaxing or shrinking the monofilament to between 91 and 76percent of the stretched length.

The extruded polypropylene monofilament may be drawn at conventionaltemperatures, i.e., between about 260 and 325 F. At about 330 F., themonofilament is approaching the molten stage, and breakage can be aproblem. The tenacity of the monofilament is somewhat higher if thedrawing is effected at the low temperature (in the-neighborhood of 260F.). Thus a product, the tensile strength of which is suitable forsuture use (tenacity 3.3 to 8.5 grams per denier), may be obtained witha draw ratio of about 6.6:] at 260-325 F. The preferred drawingtemperature for practicing the present invention is 300 F.

The relaxing of shrinking of the monofilament is also carried out at anelevated temperature, which may be within the range of the drawingtemperature, i.e., 260 to 325 F. Again, it is preferred to shrink themonofilament at a temperature of 300 F.

Monofilaments that have not contracted to 91 percent of the stretchedlength have an ultimate elongation of about 25 percent, a Young'sModulus greater than about 6X10" and are lacking in flexibility asdetermined on the Gurley'tester. F ilaments that have contracted morethan 76 percent of the stretchedlength have an excellent hand but may bedeficient in tensile strength. The preferred amount of shrinkage thatresults in a polypropylene suture of good hand and tensile strength isabout 82-85 percent.

As indicated above, a stiff or wiry suture is difficult for the surgeonto handle and tie down. A flexible suture by contrast has a "deadquality and may be characterized by the surgeon as throwable."Fortunately, the hand of the monofilament suture can be related tocertain physical characteristics that will enable one to predict itsacceptability to the surgeon independent of such subjective parametersas throwability, deadness, flexibility, or hand. One instrument that hasbeen specifically designed to measure the stifi'ness or flexibility oftextile materials is the Gurley tester. The Gurley stiffness of amonofilament suture as measured by this instrument is a measure of thedesirability of a suture from the standpoint of its handlingcharacteristics.

Other physical characteristics of polypropylene monofilaments that maybe directly related to the ease of handling by the surgeon are YoungsModulus, which is a measurement of flexibility, plastic flow, which is ameasure of extendability, yield stress data and the percent elongationat the breaking point. These properties are an indication of theacceptability of a polypropylene monofilament to the surgeon. The methodof determining these characteristics and their correlation withpliability are described below.

BRIEF DESCRIPTION OF THE DRAWING The invention will appear more clearlyfrom the following detailed description when taken in connection withthe following drawings which show by way of example a preferredembodiment of the inventive idea.

FIGS. la and lb illustrate apparatus for extruding and drawingpolypropylene monofilament in accordance with the invention.

FIG. 2 is a perspective view of two godets that draw and orient thepolypropylene monofilament.

FIG. 3 is a perspective view of the godets shown in FIG. 2 andillustrates the simultaneous drawing of four polypropylenemonofilaments.

FIG. 4 is a perspective view of a creel.

FIG. 5 is an enlarged view partially in section of the lower left leg ofthe creel as viewed from the right in FIG. 4, showing the creel in anextended position.

FIG. 6 is a sectional view of the leg of the creel illustrated in FIG.5, showing the creel in a modified position.

FIG. 7 is a sectional view of the leg of the creel illustrated in FIG.5, showing the creel in a retracted position.

FIG. 8 is a sectional view of the leg of the creel on the line 8-8 ofFIG. 5.

FIG. 9 is a perspective view of a Gurley stifiness tester.

FIG. 10 is a perspective view of a jig designed to be used with theGurley tester, and

FIG. 11 is a sectional view on the Line ll 11 of FIG. 10.

FIG. 12 is a reproduction of a stress-strain curve, obtained by applyingstress at a constant rate to a polypropylene strand that has beenproduced in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred method forpreparing the flexible polypropylene sutures of the present inventionutilizes as the raw material pellets of isotatic polypropylene having aweight average molecular weight of from about 299,000 to about 316,000and a number average molecular weight of from about 78,400 to about82,100. The computed ratio of MN,,JMW, is 3.84. Polypropylene of thisgrade is available in both powder and pellet form. Pellets, the maximumdiameter of which do not exceed one-fourth inch, may be used in theprocess to be described.

Referring now to the apparatus illustrated in FIGS. la and lb and to thephysical steps involved in extruding, orienting, and relaxing thepolypropylene monofilament, the extruder that is used to form thepolypropylene monofilament has a cylindrical barrel 11 supported in ahorizontal plane and terminating at one end at an adapter section 12which leads to an extrusion die 14. A longitudinal screw 16 is mountedfor rotation within the barrel 11 and is driven by the sprocket gear 18positioned at the end of the extruder that is remote from the diethrough the chain 19 and a variable speed motor not shown. Polypropylenepellets flow by gravity from the hopper 21 into the cylindrical barrelof the extruder and are moved by the screw 16 in the direction of thedie. The temperature of the extruder is controlled by three electricalheating units 22, 23, and 24, which surround the barrel 11 and the die14. A cooling jacket 25 surround that end of the extruder barrel that ismost remote from the die and removes heat from that end of the screw 16that lies beneath the hopper.

The die 14 is constructed with a long land length and may have one ormore orifices. Preferably, the die orifice has an entrance angle of 20.With this entrance angle, streamlined flow is obtained insuring uniformextrudate.

Polypropylene pellets, the maximum dimension of which is less thanone-fourth inch, are placed in the hopper 21 and flow by gravity intothe barrel 12 of the extruder which is at that point maintained at roomtemperature or below by water flowing through the cooling jacket 25. Thescrew 16 conveys the polypropylene pellets through the feeding zone 22into the metering zone 23 of the extruder wherein the polypropylenepellets are compressed and metered. The melted polypropylene then passesthrough the die 14, the temperature of which is controlled by a heatingjacket 24, and into a quenching bath 27, which may be a water bath. Innormal operation, the feeding zone 22 is maintained at about 430F., themetering zone 23 between 400 and 450 F., the die 14 between 400 and 450F., and the quenching bath at about 75 to 85 F.

The extruded monofilament 28 is solidified as it moves downwardly intothe quench bath. The monofilament passes around the idler 30, over theroller 32, and is wrapped around the godets 33 and 34 to prevent theslipping that might otherwise occur as a result of stretching themonofilament to orient the same and increase its tensile strength.

The monofilament from the godet 33 is stretched and oriented by passingit through the heating chamber 36 and around the godets 38 and 39 whichrotate at a higher peripheral velocity than the godets 33 and 34,thereby stretching the monofilament from six or seven times its originallength and orienting the monofilament. The manner of wrapping thepolypropylene monofilament around the godets 38 and 39 is shown in FIGS.2 and 3. FIG. 3 illustrates the arrangement of four monofilamentsextruded simultaneously through a die having four orifices. Thetemperature of the monofilament as it passes through the chamber 36 ismaintained at about 260 to 325 F.

The stretched and oriented monofilament from the godet 38 passes overthe guides 40 and the reciprocating guide 41 and is collected on spool42. The spools of polypropylene monofilament may be stored for furtherprocessing.

In the second stage processing of polypropylene, the monofilament ispermitted to shrink. This step may be carried out by a discontinuousprocess whereby a fixed length of polypropylene monofilament is heatedto about 300 F. and permitted to shrink to between 92 and 75 percent ofits original length.

The discontinuous finishing process is illustrated in FIGS. 4 through 8.The polypropylene monofilament is transferred from spool 42 to a creel43 by rotating the creel on its axle 44, power being supplied by themotor 46 through the pulleys 47 and 48 and the belt 49. The creel 43 maybe conveniently constructed of channel iron with two-leg sections 50 and52 that are welded at one end to a crossbar 53. The opposite ends ofthese leg sections slidably receive channel sections 54 and 55, whichare welded to a crossbar 57. The position of the crossbar 57 is fixedwith respect to the opposite crossbar 53 by the stay bolts 58 and 59which pass through the channel section 54 and the leg section 50.Similar bolts 58 and 59' pass through the channel section 55 and the legsection 52. The long dimension of the creel measures 50% inches whenextended as shown in FIG. 4.

After layer of polypropylene monofilament has been wound onto the creel43, a retention strip 56 is fastened to the crossbar 53 of the creel bybolts 51, thereby compressing the polypropylene monofilaments betweenthe retention strip and the end of the creel. A second retention strip56' is bolted to the opposite crossbar 57 of the creel therebypreventing the polypropylene from shifting during the heat-shrinkingstep. When the retention strips are in position, the creel is supportedon its axle 44 with the movable crossbar 57 of the creel in itslowermost position, and the stay bolts 58, 59, 58 and 59 are removedfrom each leg of the creel. The channel sections 54 and 55 are thentelescoped into the legs 50 and 52 a distance corresponding to thedesired amount of shrinkage and the stay bolts replaced. The creel isthen placed in an oven maintained at 300 F. and rotated at 5-20 r.p.m.to insure uniform heating. At this temperature, the polypropylene thatis wrapped on the creel shrinks causing the channel sections 54 and 55of the creel to telescope into the leg sections 50 and 52 as indicatedby FIG. 6. The creel is removed from the oven after 10 minutes and ispermitted to cool to room temperature. The position of the end 57 of thecreel after the heatshrinking step is shown in FIG. 7. As indicatedabove, the creel in its extended position (FIG. 5) has a length of 50%inches, which may be reduced to 42 inches (FIG. 7) after shrinkage ofeach 505a-inch length of polypropylene amounts to 8% inches (from 50%inches to 42 inches in increments that permit shrinking of themonofilament from 91 to 75.6 percent.

Straight polypropylene monofilaments 42 inches in length are removedfrom the creel by cutting the filaments at the opposite ends 53 and 57of the creel. Needles may be swaged to one end of the monofilaments soobtained. The heat-relaxed monofilaments with or without needlesattached thereto are cooled, packaged, and sterilized for use assurgical sutures.

The present invention will be further illustrated by the followingexamples which describe the manufacture of polypropylene sutures (size 2through 7/0) and the physical properties thereof. In all of thefollowing examplesisotatic polypropylene is used having a weight averagemolecular weight of between about 294,000 and about 316,000 and a numberaverage molecular weight of between about 78,400 and about 82,100. Tothis resin is added 0.5 percent by weight of copper phthalocyanine dye,which imparts a dark blue color to the resin and the monofilamentsextruded therefrom.

Heat stabilizers and other processing compounds known in the art may beadded to improve the resistance to oxidation during the extrusion andprocessing steps. Compounds commonly used for this purpose are tertiarybutyl-o-cresol (IONOL) together with dilauryl thio-propionate in amountsof about 0.25 percent each.

The tensile strength and percent elongation at break reported inexamples I through XIII are determined by A.S.T.M. method D225666T usinga constant rate of extension tester, namely a table model INSTRONuniversal testing instrument manufactured by the Instron Corporation ofCanton, Massachusetts. This test method is described in the 1966 Book ofA.S.T.M. Standards, part 24 (published in Aug. of 1966 by the AmericanSociety for Testing Material, I916 Race Street, Philadelphia,Pennsylvania). The 20 seconds to break is approximated by using a 1-inchsample (or gauge length) with the INSTRON Tester crosshead speed set at1 inch per minute.

The knot strength is determined by the test method described in the US.Pharmacopeia, Vol. XVII, page 921.

Young's Modulus is detennined on a Table Model lN- STRON instrumentusing line contact jaw faces to minimize slippage. A 10.0-inch sample iselongated at the rate of 5.0

inches per minute (crosshead speed), the chart speed is 20.0

inches per minute. lt has been noted that the pliability of apolypropylene suture may be correlated with its behavior under stress.Physical tests that may be used to reliably evaluate the subjectivecharacteristics of "hand," flexibility, and extensibility are describedin example I.

The Gurley stiffness is measured with a motor-operated Gurley StiffnessTester (Model 4171) manufactured by W. and L.. E. Gurley of Troy, NewYork. This instrument, illustrated in FIG. 9, consists of a balancedpendulum or pointer 60, which is center pivoted and which can bevariously weighted below itscenter with a removable weight 61. Thepointer moves parallel to a sine scale 62 graduated in both directions.In the test, 10, 2-inch polypropylene monofilament strands, a total ofat least 20 inches, are required per sample. The strands used should berelatively straight.

The 10, 2-inch strands 63 are inserted in the jig illustrated in FIGS.and 11. The jig is constructed with 10 parallel holes drilled on )-inchcenters. The polypropylene strands are inserted so that at least I inchof each strand protrudes beyond the bending bar 64, and a locking pin 65is inserted to clamp the monofilaments in the jig.

A razor blade is used to shave closely the strand tips which extend fromthe back of the jig, and all 10 strands are cut 1 inch from the edge ofthe bending bar 64 on the opposite side of the clamp.

The jig is placed on the motor-driven arm 68 of the Gurley instrument sothat the clamp-bending bar lies one-half inch above the edge 70 of theswinging pendulum. When the motor-driven arm 68 presses themonofilaments 63 against the edge 70 of the pendulum, the pointer isdeflected until the sample scrapes past the pendulum and may be read onthe scale 62. The resistance of the pendulum and thus the sensitivity ofthe machine to materials of different stiffness can be adjusted in twoways: by changing the distance from the fulcrum 67 of the weight 61 andby changing the weight itself.

The machine is operated for one or two cycles to adjust theweight-distance combination if necessary. This adjustment should be madeso that the average reading will fall between 2.0 and 7.0 Gurley units.(A cycle is defined as a left plus a right swing of the pointer 60. AGurley unit is the unit reading marked on the sine scale). After thenecessary adjustments are made, the machine is operated for 10 cycleswithout recording the results. After each half cycle, the oscillation ofthe pendulum is stopped before continuing. The readings of cycles 11through 15 are recorded and averaged. The stiffness of the polypropylenemonofilament sample may then be calculated by use of the followingformula:

Gurley stiffness (mg) 0.0002 RWD, where R test reading in Gurley units Wcounterweight (g.) D distance of counterweight from fulcrum (inches) Thepresent invention will be further illustrated by the following exampleswhich describe the manufacture of polypropylene sutures of differentsizes, all of which have a Youngs Modulus below 6 l0 p.s.i. and anelongation at break.of at least 35 percent.

EXAMPLE I All Viscoelastic measurements reported in the tables are madeon a Table Model lNSTRON Tensile Tester using a Type C Tension Cell;full-scale range 1 to 50 pounds. The measurements are made in anair-conditioned laboratory at 72 F. and 50 percent relative humidity. Tohold the specimen suture strand, two line contact jaws are used. Thediameter of the strand is measured to 0.0001 inches and the area of thestrand is calculated. A 10-inch sample is placed between the jaws andboth jaws closed, under 20 p.s.i. air pressure. The area compensator onthe lNSTRON Tester is set for the correct diameter of the suture (togive readout in p.s.i.) and the strand is elongated at a constant rateto 122.5 percent of the original length (preset on the lNSTRON). ThelNSTRON machine is operated at a crosshead speed of 5 inches per minuteand a chart speed of 20 inches per minute.

Stress-strain curves produced under these conditions have the generalshape illustrated in FIG. 12. Youngs Modulus (p.s.i. X 10 is the initialmodulus as determined from the slope of the curve A of FIG. 12. Young'sModulus is the ratio of applied stress to strain in the elastic regionand measures the elastic component of a suture's resistance to stress.This value is related to the flexibility of a suture.

Plastic flow (p.s.i. X 10) is the viscoelastic modulus as determinedfrom the slope of the curve B of FIG. 12. It measures the plasticcomponent of a sutures resistance to stress and is related to the "givea suture exhibits under a force in excess of the yield stress.

The yield stress (p.s.i. X 10) is the first point of inflection in thestress-strain curve or the point of intersection C of the slopes A and Bof FIG. 12. Yield Stress measures the force required to initiateviscoelastic flow and is related to the straightenability of a suture.

Typical pliability data as determined from the stress-strain curves ofthe polypropylene sutures of the present invention is summarized intable I. The date is obtained after aging the sample for 1 month.

A size 7/0 polypropylene suture, diameter 2.6 mils, is prepared by thegeneral procedure described above. The die orifice measures 20 mils indiameter, and the flow rate of the polypropylene through the die orificeis 0.06 pounds per hour. The temperature of the feed zone is maintainedat 430 F., and the temperature of the die and extruder barrel ismaintained at 450 F. The ratio of the rate of takeup of the godet 33 tothe linear rate of extrusion (draw ratio) is 5.9. The water bath ismaintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 285 F., asmeasured with a pyrometer. The polypropylene monofilament enters thechamber at the linear rate of 50 feet per minute andjis taken up on thegodet 38 at the linear rate of 330 feet per minute (stretched 6.6 timesits original length). The propylene monofilament after hot stretching iscollected on the takeup spool 42 and transferred to the creel 43illustrated in FIGS. 4-8. The tension strips are applied to either endof the creel and the distance between the crossbars 53 and 57 isadjusted by the stay bolts 58, 59, 58' and 59 to permit the desiredamount of shrinkage. The creel is then heated in an oven at 285 F. androtated at 10 r.p.m. for 10 minutes; during which time the monofilamentshrinks to 5% times its original length (from 50% to 42 inches or 83.5percent).

in a control experiment, polypropylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. for 10minutes with no relaxation. The length of the monofilament is 52% inchesprior to and after the 10 minutes heat treatment at 300 F. The followingtable shows the differences in the physical properties of polypropylenemonofilament that has been (1) hot stretched 6.6 X while maintaining thetemperature at 285 F.; (2) hot stretched 6.6 X its original length whilemaintaining the temperature at 285 F. and then annealing for l minutesat 300 F. without relaxation; and (3) hot stretched 6.6 X its originallength while maintaining the temperature at 285 F. and the annealing for10 minutes at 300 F. while relaxing to 5.5 X its original length (83.5percent of its hot stretched length). The data is obtained after agingthe samples for 1 month.

TABLE ll (2) Polypropyl- (3) lolypro yiene stretched one stretc red (1)Poly- 6.6:1nnd 6.621 and propylene nnneuled at relnxcd to 83.5%stretched 300 F. for of stretched 6.5:1 10 min. length Lot number 115325115325 115325 Diameter, mils 2. 4 2.3 2. 6 Denler....... 24 22 .38Tensile strength:

Grams/denier n. X 8. 8. ll P.s.l.X 11.26 12.15 10.16 Knot strcn th:

Grams denier 7. 7 8.8 7. J P.s.i.X10' 8.83 0.28 0.03 Break elongation,

percent 27 37 ii (Inrlcy stiflness, rng... 1 l l Young's modulus,p.s.isoxim 8.03X10 -l.-li)Xl0 EXAMPLE [ii A size 5/0 polypropylenesuture, diameter 4.9 mils. is prepared by the general proceduredescribed above. The die orifice measures mils in diameter, and the flowrate of the polypropylene through the die orifice is 0.09 pounds perhour. The temperature of the feed zone is maintained at 430 F.. and thetemperature of the die and extruder barrel is maintained at 450 F. Theratio of the rate of takeup of the godet 33 to the linear rate ofextrusion (draw ratio) is 2.32. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 285 F. asmeasured with a pyrometer. The polypropylene monofilament enters thechamber at the linear rate of 30 feet per minute and is taken up on thegodet 38 at the linear rate of 198 feet per minute (stretched 6.6 timesits original length). The polypropylene monofilament after hotstretching is collected on the takeup spool 42 and transferred to thecreel 43 illustrated in FIGS. 4-8. The tension strips are applied toeither end of the creel and the distance between the crossbars $3 and 57is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desiredamount of shrinkage. The creel is then heated in an oven at 285 F. androtated at 10 r.p.m. for ID minutes; during which time the monofilamentshrinks to 5 V2 its original length (from 50% to 42 inches or 83.5percent).

In a control experiment, propylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. for l0minutes with no relaxation. The length of the monofilament is 52% inchesprior to and after the 10- minute heat treatment at 300 F. The physicalproperties of the product so obtained are summarized in the followingtable. The data is obtained after aging the samples for l month.

EXAMPLE IV A size 4/0 polypropylene suture, diameter 6.9 mils, isprepared by the general procedure described above. The die orificemeasures 34 mils in diameter, and the flow rate of the polypropylenethrough the die orifice is 0.24 pounds per hour.

TABLE III (1) Polypropyl- (3) lolyprn xylene strutc red enrsire! v ltil(l) Poly 6.621 and 6.6:1 nmi propylene nnnenled ut i't'lnserl to $3.5";stretched 300 F. for of stretched 6.6:]. 10min. length Lot llllillbtL.107M251 107925 1071 125 llinmet er, mils. -i. ll 5. n 5. '3 Denier"....IS 10'. ill Tensile strength:

(il'tliliS/tltllltl'. (i. 5 ii. 7 5. 7 1.s.i.Xl0-- T. 4;! 7. 63 (L511Knot strength:

(lrnins/denier. 5. S 5. l 4 l.s.l.Xl0 ti. 0'. ti. '..'i ii. 2i llrenkelongation.

percent. '27 30 3S Hurley stiilness. lllll. 4. l 3. -l 3. l Youngsmodulus. p.s.l. 7. 15x10 6. 411x10 142x10 the temperature of the die andextruder barrel is maintained at 430 F. The ratio of the rate of takeupof the godet 33 to the linear rate of extrusion (draw ratio) is 3.62.The water bath is maintained at -84 F. The data is obtained afler agingthe samples for l month.

The heating chamber is 7 feet in length and is maintained at 295 F. asmeasured with a pyrometer. The polypropylene monofilament enters thechamber at the linear rate of 40 feet per minute and is taken up on thegodet 38 at the linear rate of 264 feet per minute (stretched 6.6 timesits original length). The polypropylene monofilament after hotstretching is collected on the takeup spool 42 and transferred to thecreel 43 illustrated in FIGS. 4-8. The tension strips are applied toeither end of the creel and the distance between the crossbnrs 53 and 57is adjusted by the stay bolts 58. 59. 58 and 59' to permit the desiredamount of shrinkage. The creel is then heated in an oven at 300 androtated at l0 r.p.m. for 10 minutes; during which time the monofilamentshrinks to 5% times its original length (from 50% to 42 inches or 83.5percent).

ln a control experiment, polypropylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. androtated at l0 r.p.m. for l0 minutes with no relaxation. The length ofthe monofilament is 52% inches prior to and after the lO-minutc heattreatment at 300 F. The difl'erence in the physical properties ofpolypropylene monofilament that has been drawn, annealed withoutrelaxation and heat relaxed to 83.5 percent of its original length issummarized in the following table. The data is obtained after aging thesample for 1 month.

TABLE i\' (2) lolypropyl- (Ii) lolypro )ylone strctc red one strete red(1) loly- 6.011 nnd tl.ti:l and propylene annealed at r'elnxed to 83.6?stretched for oistretchcd 6.6:l l0 rnln. length Lot uumher.. 107930107M110 1071 30 Dinmeter, inlls.... 6. 1| 13.5 7.1 l enier........ 1941241i 223 Tensile strength:

Grunts/denier... 5. 7 n T 5 I l.s.l.Xl0- 7 7.- T 70' ill Knot strength:

Grains/denier... 4.4 4.7 1.5 i'.s.l.Xl0' 5.08 5.37 b. llrenk elongntlon,

percent. L'] 28 30 Hurley stillness, mg. 15.5 11.4 IL. 4 Young'smodulus, p.s.i. ti. x10 10x10 1 l8 10 EXAMPLE V A size 3/0 polypropylenesuture, diameter 8.6 mils, is prepared by the general proceduredescribed above. The die orifice measures 34 mils in diameter, and theflow rate of the polypropylene through the die orifice is 0.24 poundsper hour. The temperature of the feed zone is maintained at 430F.. and

The temperature f the f d long is maintain; at 430 [and the temperatureof the die and extruder barrel is maintained at 430 F. The ratio of therate of takeup of the godet 33 to the linear rate of extrusion (drawratio) is 2.26. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 260 F. asmeasured with a pyrometer. The polypropylene monofilaments enters thechamber at the linear rate of 25 feet per minute and is taken up on thegodet 38 at the linear rate of 165 feet per minute (stretched 6.6 timesits original length). The polypropylene monofilament after hotstretching is collected on the takeup spool 42 and transferred to thecreel 43 illustrated in FIGS. 4-8. The tension strips are applied toeither end of the creel and the distance between the crossbars 53 and 57is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desiredamount of shrinkage. The creel is then heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes; during which time the monofilamentshrinks to 5% times its original length (from 50% to 42 inches or 83.5percent).

In a control experiment, polypropylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes with no relaxation. The length ofthe monofilament is 52% inches prior to and after the l-minute heattreatment at 300 F. The difference in the physical properties ofpolypropylene monofilament that has been drawn, annealed withoutrelaxation and heat relaxed to 83.5 percent of its original length issummarized in the following table. The data is obtained after aging thesamples for 1 month.

TABLE V 'Gurley stiffness, mg.-.

(3) Polypropylp p py ed ene stretche ene stretch 6.6:1 and annealed at300 F. for 10 min.

(1) Polypropylene stretched 6.6:1

25 20. 0 Young's modulus, psi. 8. 21X10 6.6:1 and relaxed to 83.5% ofstretched length EXAMPLE VI A size 2/0 polypropylene suture, diameter 11.1 mils, is prepared by the general procedure described above. The dieorifice measures 54 mils in diameter, and the flow rate of thepolypropylene through the die orifice is 0.60 pounds per hour. Thetemperature of the feed zone is maintained at 430 F., and thetemperatures of the die and extruder barrel is maintained at 430 F. Theratio of the rate of takeup of the godet 33 to the linear rate ofextrusion (draw ratio) is 3:33. The water bath is maintained at 75-84 F.

The heating chamber is to 7 feet in length and is maintained at 230 F.as measured with a pyrometer. The polypropylene monofilament enters thechamber at the linear rate of 38 feet per minute and is taken up on thegodet 38 at the linear rate of 250 feet per minute (stretched 6.6 timesits original length). The polypropylene monofilament after hotstretching is collected on the takeup spool 42 and transferred to thecreel 43 illustrated in FIGS. 4-8. The tension strips are applied toeither end of the creel and the distance between the crossbars 53 and 57is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desiredamount of shrinkage. The creel is then heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes; during which time the monofilamentshrinks to 5 A its original length (from 50% to 42 inches or 83.5percent).

In a control experiment, polypropylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes with no relaxation. The length ofthe monofilament is 52% inches prior to and after the IO-minute heattreatment at 300 F. The difference in the physical properties ofpolypropylene monofilament that has been drawnannealed withoutrelaxationand heat relaxed to 83.5 percent of its original length is summarized inthe following table. The data is obtained after aging the samples for 1month.

TABLE VI (2) polypropyl- (3) Polypropylene stretched one stretched (1)loly- 6.6:1 and 6.6:1 and propylene annealed at relaxed to 83.6%stretched 300 F. for of stretched 6.6:1 10 min. length Lot number 115358115358 115358 11. 1 11.3 12. 4 Denier 603 521 627 Tensile strength:

Grams/denier. 5. 4 5.7 4. X 'l.s.l. 10- (l. 1'.) ll. 48 5. 4t) Knotstrength:

Grams/denier. 3. ll 3. .l 3. 5 l.s.l.) 10* 4. 44 4.48 4. 05 Breakelongation,

percent 25 34 38 Gurley stiffness, mg 68.0 55. 0 61.0 Youngs modulus,p.s.i 6. 48X10 6. lJfiXlO 4. 015x10 EXAMPLE VII A size of 0polypropylene suture, diameter 13.8 mil, is prepared by the generalprocedure described above. The die orifice measures 54 mils in diameter,and the flow rate of the polypropylene through the die orifice is 0.59pounds per hour. The temperature of the feed zone is maintained at 430F., and the temperature of the die and extruder barrel is maintained at430 F. The ratio of the rate of takeup of the godet 33 to the linearrate of extrusion (draw ratio) is 2.22. The water bath is maintained at-84 F.

The heating chamber is 7 feet in length and is maintained at 240 F. asmeasured with a pyrometer. The polypropylene monofilament enters thechamber at the linear rate of 25 feet per minute and is taken up on thegodet 38 at the linear rate of feet per minute (stretched 6.6 times itsoriginal length). The polypropylene monofilament after hot stretching iscollected on the takeup spool 42 and transferred to the creed 43illustrated in FIGS. 4-8. The tension strips are applied to either endof the creel and the distance between the crossbars 53 and 57 isadjusted by the stay bolts 58, 59, 58' and 59' to permit the desiredamount of shrinkage. The creel is then heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes; during which time the monofilamentshrinks to 5% times its original length (from 50% to 42 inches or 83.5percent.). 1

In a control experiment, polypropylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes with no relaxation. The length ofthe monofilament is 52% inches prior to and after the 10-minute heattreatment at 300 F. The difference in the physical properties ofpolypropylene monofilament that has been drawn annealed withoutrelaxation and heat relaxed to 83.5 percent of its original length issummarized in the following table. The data is obtained after aging thesamples for 1 month.

EXAMPLE VIII A size 1 polypropylene suture, diameter 16.1 mil, isprepared by the general procedure described above. The die orificemeasures 54 mils in diameter, and the flow rate of the polypropylenethrough the die orifice is 0.80 pounds per hour. The temperature of thefeed zone is maintained at 430 F., and the temperature of the die andextruder barrel is maintained at TABLE VII p yp pylene stretched (3)Polypropylene stretched (1) Poly- 6.621 and 6.611 and propylene annealedat relaxed to 83. 5% stretched 300 F. for of stretched 6.6:1 10 min.length Lot number 107947 107947 107947 Diameter, mils 13. 8 14.0 14.8i.D en

773 798 8 4 Tensile strength:

Gra ns/denier 5. 1 5. 3 4. 7 P.s.r.X10 5.88 6.04 5.40 Knot strength:

Grams/denier 3. 8 3. 9 3. 4 P.s.i. 10- 4.41 4.41 3. 95 Break elongation,

percent 27 36 53 Gurley stiffness, mg. 159.0 134. 124. 0 Young'smodulus, psi- 6. 33x10 5. 73x10 3. 54X10 430 F. The ratio of the rate oftakeup of the godet 33 to the linear rate of extrusion (draw ratio) is1.61. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 255 F. asmeasured with a pyrometer. The polypropylene monofilament enters thechamber at the linear rate of 23 feet per minute and is taken up on thegodet 38 at the linear rate of 152 feet per minute (stretched 6.6 timesits original length). The polypropylene monofilament after hotstretching is collected on the takeup spool 42 and transferred to thecreel 43 illustrated in FIGS. 4-8. The tension strips are applied toeither end of the creel and the distance between the crossbars 53 and 57is adjusted by the stay bolts 58, 59, 58' and 59 to permit the desiredamount of shrinkage. The creel is then heated in an oven at 300 F. androtated at r.p.m. for 10 minutes; during which time the monofilamentshrinks to 5% times its original length (from 50% to 42 inches or 83.5percent).

ln a control experiment, polypropylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes with no relaxation. The length ofthe monofilament is 52% inches prior to and after the lO-minute heattreatment at 300 F. The difference in the physical properties ofpolypropylene monofrlament that has been drawn annealed withoutrelaxation and heat relaxed to 83.5 percent of its original length issummarized in the following table. The data is obtained after aging thesamples for 1 month.

TABLE VIII (2) polypropyl- (3) Polypropylone stretched ene stretched (1)Poly- 6.6:1 and 6.6:1 and propylene annealed at relaxed to 83.57stretched 300 F. for of stretched 6.6:1 10 min. length Lot number 107942107042 107942 Diameter, mils- 16. l 16. 4 18. 1 Denier. 1,058 1,0971,339 Tensile strength:

Grams/denier 5. 2 5. 2 4. 4 I.S.i.X10- 5. 00 5.86 5.01 Knot strength:

Grams/denier. 3. 8 3. 7 3. 4 P.s.i.Xl0- 4.37 4.21 3.88 Break elongation,

percent 31 40 51 Gurley stillness, mg. 262. 0 240. 0 232. 0 Young'smodulus, p.s.i 6. 25X10 5. 72X10 3. 13x10 EXAMPLE 1x A size 2polypropylene suture, diameter 19.4 mils is prepared by the generalprocedure described above. The die orifice measures 64 mils in diameter,and the flow rate of the polypropylene through the die orifice is 1.1pounds per hour. The temperature of the feed zone is maintained at 430 Fand the temperature of the die and extruder barrel is maintained at 430F. The ratio of the rate of takeup of the godet 33 to the linear rate ofextrusion (draw ratio) is 1.70. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 230 F. asmeasured with a pyrometer. The polypropylene monofilament enters thechamber at the linear rate of 26 feet per minute and is taken up on thegodet 38 at the linear rate of 168 feet per minute (stretched 6.6 timesits original length). The polypropylene monofilament after hotstretching is collected on the takeup spool 42 and transferred to thecreel 43 illustrated in FIGS. 4-8. The tension strips are applied toeither end of the creel and the distance between the crossbars 53 and S7is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desiredamount of shrinkage. The creel is heated in an oven at 300 F. androtated at l0 r.p.m. for 10 minutes; during which time the monofilamentshrinks to 5% times its original length (from 50% to 42 inches or 8.35percent).

in a control experiment, polypropylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes with no relaxation. The length ofthe monofilament is 52% inches prior to and after the 10-minute heattreatment at 300 F. The difference in the physical properties ofpolypropylene monofilament that has been drawn, annealed withoutrelaxation and heat relaxed to 83.5 percent of its original length issummarized in the following table. The data is obtained after aging thesamples for 1 month.

TABLE 1X (2) polypropyl- (3) Polypropylcne stretched enusin-tolled (1)loly- 60:1 and (5.0:1 and propylene annealed at I'l'lflXLLl to 83.5%stretched tor of stretched 6.6:1 10 min. length Lot number 115351 115351115351 Diameter, mils. ll). 4 111.4 20. 5 l)onlcr 1,536 1,536 1.714Tensile strength:

Grams/denier... 4. 2 4.11 .1. u 1.s.l. 10 4. 5. 24 4. 44 Knot strength:

Grams/denier... 3. 0 3. it 1!. 3 1.s.l.X10- 3.45 3. 7'. 3. 51 Breakelongation.

percent 34 37 0'3 (lurley stillness, mg. 370. 7 3112.0 3128.0 Young'smodulus, psi. 5. 4TX10 4. 07x10 3. 313x10 EXAMPLE X A size 3/0polypropylene suture, diameter 9.14 mils, is prepared by the generalprocedure described in example V. Instead of stretching thepolypropylene monofilament 6.6 times, however, it is stretched 6.0 timesits original length in a heating chamber maintained at 260 F.

The polypropylene monofilament after hot stretching is collected on thetakeup spool 42 and transferred to the creel 43 illustrated in FIGS.4-8. The tension strips are applied to either end of the creel and thedistance between the crossbars 53 and 57 is adjusted by the stay bolts58, 59, 58 and S9 to permit the desired amount of shrinkage. The creelis then heated in an oven at 300 F. and rotated at 10 r.p.m. for 10minutes; during which time the monofilament shrinks to 5% times itsoriginal length (91.6 percent).

In a control experiment, polypropylene from the same extrusion batch(stretched 6.0 times its original length) is removed from the takeupspool 42, placed on the creel and heated in an oven at 300 F. androtated at 10 r.p.m. for l0 minutes with no relaxation. The length ofthe monoiilament is 52% inches prior to and after the lO-minute heattreatment at 300 F.

The difference in the physical properties of polypropylene monofilamentthat has been drawn, annealed without relaxation and heat relaxed to91.6 percent of its stretched length is summarized in the followingtable. The data is obtained after aging the samples for 1 month.

TABLE X Polypropylene Polypropylene stretched 6.0: 1 Polystretched 6.0:1 and relaxed propylene and annealed to 91.6% of stretched at 300F. forstretched 6.0: 1 10 min. length Lot number 127642-141 127642-A2127642-A3 Diameter, mils. 9. 14 9. 15 0. 61 Denier 341 342 376 Tensilestrength:

Grams/denier. 4. 7 5. 3 4. 8 P.s.1.X10 5.44 6.06 5.47 Knot strength:

Grams/denier 3. 5 4. 1 4. P.s.i.X10- 4. 04 4. 66 4. 53 Break elongation,percent 26 36 37 Gurley stillness, mg. 31. 3 26. 28.0 Youngs modulus,p.s.i 8. 95X10 7. 76x10 6. 27x10 EXAMPLE Xl A size 3/0 7 suture,diameter 8.84 mils, is prepared by the general procedure described abovein example V. Instead of stretching the polypropylene monofilament 6.6:]however, it is stretched 7 times its original length in a heatingchamber maintained at 260 F. The polypropylene monofilament after hotstretching is transferred to the creel 43 illustrated in FIGS. 4-8 andpermitted to shrink to 5.5 times its stretched length by heating forminutes at 300 F.

In a control experiment, polypropylene from the same extrusion batch(stretched 7.0 times its original length) is removed from the takeupspool 42, placed on the creel and heated in an oven at 300 F. androtated at 10 r.p.m. for 10 minutes with no relaxation. The length ofthe monofilament is 52% inches prior to and after the 10-minute heattreatment at 300 F.

The difi'erence in the physical properties of polypropylene monofilamentthat has been drawn, annealed without relaxation, and heat relaxed to78.5 percent of its stretched length is summarized in the followingtable. The data is obtained after aging the samples for l month.

TABLE XI Polypropylene Polypropylene stretched 7 .0:1 Polystretched 7.0:1 and relaxed propylene and annealed to 78.6% of stretched at 300 F.for stretched 7.0: 1 10 min. length Lot number 127642-01 127642-C2127642-03 Diameter, mils. 8. 54 8. 45 0. 60 Denier 298 291 376 Tensilestrength:

Grams/denier. 6.0 5. 3 4. 7 P.s.i. 10- 6. 82 6.08 5. 41 Knot strength:

Grams/denier. 3. 9 4. 1 3. 8 P.s.i.X10' 4.41 4. 70 4.33 Breakelongation, p

cent 25 H 41 Gurley stillness, mg. 22. 7 22. 5 21. 2 Young's modulus,p.s.i. 11. 23X10 9. 35x10 6. 16x10 EXAMPLE Xll A size 0 polypropylenesuture, diameter 13.9 mils, is prepared by the general proceduredescribed above in example VII. The die orifice measures 54 mils indiameter, and the flow rate of the polypropylene through the die orificeis 0.59 pounds per hour. The temperature of the feed zone is maintainedat 430 F., and the temperature of the die and extruder barrel ismaintained at 430 F. The ratio of the rate of takeup of the godet 33 tothe linear rate of extrusion (draw ratio) is 2.22. The water bath ismaintained at 7S-84 F.

The heating chamber is 7 feet in length and is maintained at 240 F. asmeasured with a pyrometer. The polypropylene monofilament enters thechamber at the linear rate of 25 feet per minute and is taken up on thegodet 38 at the linear rate of 165 feet per minute (stretched 6.6 timesits original length). The polypropylene monofilament after hotstretching is collected on the takeup spool 42 and transferred to thecreel 43 illustrated in FIGS. 4-8. The tension strips are applied toeither end of the creel and the distance between the crossbars 53 and 57is adjusted by the stay bolts 58, 59., 58' and 59' to pennit the desiredamount of shrinkage. The creel is then heated in an oven at 300 F. androtated at 10 r.p.m. for l0 minutes; during which time the monofilamentshrinks to 6.0 times its stretched length.

In a control experiment, polypropylene from the same extrusion batch(stretched 6.6 times its original length) is removed from the takeupspool 42, placed on the creel, and heated in an oven at 300 F. androtated at l0 r.p.m. for 10 minutes with no relaxation. The length ofthe monofilament is 52% inches prior to and after the 10-minute heattreatment at 300 F. The difference in the physical properties ofpolypropylene monofilament that has been drawn, annealed withoutrelaxation and heat relaxed to 9l percent of its stretched length issummarized in the following table. The data obtained after aging thesample for 1 week is as follows.

TABLE XII Polypropylene stretched 6.6:1 and annealed at 300 F. for 10min.

Polypropylene stretched 6.6:] and relaxed to 91% of stretched lengthPoly ropy cne stretched 6.6:1

Lot number Diameter, mils. Denier Tensile strength:

Gra ns/denier Break elongation, percent Gurley stiffness, mg...

Young's modulus, p.s.i.

23 25. 0 1'38. 0 .L 78X10 5. 23X 10 EXAMPLE Xlll TABLE XIIIPolypropylene Polypropylene Poly rostretched 6.6:1 stretched 6.6:1 pyene and annealed at and relaxed to stretched 300 F. for 10 111% of 6.6:1min. stretched length Lot number 1108051) 127042-0 2 1108421) Diameter,mils. 13.0 8. 45 15.11 Denier 788 201 'JEI. Tensile strength:

Grams/denier... 5.1 5.3 4.2 P.s.i.X1O- 5. 86 ii. 08 -l. 81 Knotstrength:

Grams/denier... 3.8 1. 1 3. 3 P.S.i.Xl0 4. 35 4. 70 3. 70 Breakelongation, perctl'lt 27 Z3 50 (.lurley stillness, n1g. 148. 0 25. 0132. 0 Young's modulus. psi. 6. 72x10 0. 78X1U 3 31x10 While bothmonofilament and braided multifilament sutures are commonly used in theoperating room, the monofilament structure is preferred by manysurgeons. Polypropylene monofilament sutures prepared as described aboveare easy to use and tie because of their flexibility. The polypropylenesutures may be attached to surgical needles, sterilized with ethyleneoxide and packaged in sterile containers for use in the operating room.

What is claimed is:

1. An isotactic polypropylene monofilament suture the diameter of whichis in the range of from about 0.002 to about 0.020 inches, saidisotactic polypropylene having the following characteristics:

Weight Average Molecular Weight Number Average Molecular Weight TensileStrength Knot Strength Break Elongation 2. A needled surgical suturecomprising an isotactic about 294.000 to about 3l6,000

about 78.400 to about 82.]

3.9 to 8.9 gratin/denier 3 3 to 7.9 grams/denier 36% to 62%polypropylene suture attached to a surgical needle, said needle and saidsuture being sterile, said isotactic polypropylene having approximatelythe following characteristics:

Weight Average Molecular Weight Number Average Molecular Weight TensileStrength 7 Knot Strength about 294,000 to about 3l6,000

about 78,400 to about 82,l00

3.9 to 8.9 grams/denier denier 3.3 to 7.9 grams/denier Break Elongation36% to 62% Young! Modulus about 3.l3Xl0' p.|.i. to

Weight Average Molecular Weight about 294,000 to about 6,000 NumberAverage Molecular Weight about 78,400 to about 82.l00 Tensile Strength3.9 to 8.9 grams/denier Knot Strength 3.3 to 7.9 grarmldenier BreakElongation 36% to 62% Young's Modulus about 3.l3 l0' p.:.i. to

mg UNITED STATES PATENT oEElcE CERTIFICATE OF CORRECTION Patent No.3,630,205 Dated December 28,1971

Inventor(s) Gr gory J. Listner It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

T- Column 3, line 23, "surround" should read surrounds 1 Column 6, line6, "122.5" should read 112.5

Column 7, line 59, 5 1/2 should read ---5 1/2 times Column 8, line 35,"300" should read 300%.

Column 9, line 61, "is to 7 feet" should read 1 1-- is 7 feet Column 9,line 7 "5 1/2" should read 5 1/2 times Column 10, line +8, creed" shouldread ---creel Column 12, line 1 8.35: should read 83.5

Column 1.3,line 19, "3/0 7" should read 3/0 polypropylene ture Signedand sealed this 1 8th day of July 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. A needled surgical suture comprising an isotactic polypropylenesuture attached to a surgical needle, said needle and said suture beingsterile, said isotactic polypropylene having approximately the followingcharacteristics: Weight Average Molecular Weight about 294,000 to about316,000 Number Average Molecular Weight about 78,400 to about 82,100Tensile Strength 3.9 to 8.9 grams/denier denier Knot Strength 3.3 to 7.9grams/denier Break Elongation 36% to 62% Young''s Modulus about 3.13 X105 p.s.i. to about 5.23 X 105 p.s.i.
 3. A surgical suture packagecomprising a sterile enclosure and therein a sterile needled surgicalsuture comprising an isotactic polypropylene suture attached to thesurgical needle, said isotactic polypropylene having approximately thefollowing characteristics: Weight Average Molecular Weightabout 294,000toabout 316, 000Number Average Molecular Weightabout 78,400 toabout 82,100Tensile Strength3.9 to 8.9 grams/denierKnot Strength3.3 to 7.9grams/denierBreak Elongation36% to 62%Young''s Modulusabout 3.13 X 105p.s.i. toabout 5.23 X 105 p.s.i.